1. Field of Invention
The present invention relates generally to an imaging process. More specifically, the invention relates to an apparatus and method in which a liquid is applied to a support surface, such as an intermediate transfer drum, of the imaging system, and in which liquid removed from the support surface is recycled.
2. Description of Related Art
Ink jet printing systems have utilized intermediate transfer surfaces, such as that disclosed in U.S. Pat. No. 4,538,156 to Durkee et al. This patent discloses a system wherein an intermediate transfer drum is employed with a print head. The surface of the transfer drum may be of a plastic material, such as teflon, tefzel, mylar or the like. In addition, smooth metal or ceramic surfaces can be used. A final receiving surface of paper is brought into contact with the intermediate transfer drum after the image has been placed thereon by the nozzles in the print head. The image is then transferred to the final receiving surface. A cleaning medium is then brought into contact with the intermediate transfer drum to prepare the surface of the drum prior to the next image being formed on the transfer surface.
U.S. Pat. No. 5,099,256 to Anderson describes an intermediate drum with a surface that receives ink droplets from a print head. The intermediate drum surface is thermally conductive and formed from a suitable film-forming silicone polymer allegedly having a high surface energy and high degree of surface roughness to prevent movement of the ink droplets after receipt from the print head nozzles. Anderson teaches that the film-forming silicone polymer coating on the surface of the intermediate drum enables substantially complete transfer of the dehydrated ink droplets therefrom to a recording medium, so that the removal of residual ink from the drum surface by the cleaning means, such as a blade, is unnecessary. The teaching of Anderson, however, does not show how the film-forming silicone polymer is applied to the intermediate drum surface.
U.S. Pat. No. 5,389,958 to Bui et al. discloses an offset ink jet printing system in which a liquid intermediate transfer surface is applied to the transfer drum. Nozzles in the print head then eject drops of ink onto the liquid intermediate transfer surface to form an ink image thereon. A final receiving substrate such as paper is then brought into contact with the intermediate transfer surface, and the ink image is transferred to the final receiving substrate. The liquid intermediate transfer surface is cleaned and reapplied prior to the next image being formed on the transfer surface.
Ink jet printing systems that utilize a liquid intermediate transfer surface generally require an applicator to apply the desired amount of liquid onto the intermediate transfer support surface. An exemplary applicator of this type is disclosed in U.S. Pat. No. 5,808,645 to Reeves et al. (hereinafter “the 645” patent). This patent discloses an applicator that is housed in a replaceable transfer drum maintenance cassette. The applicator uses a wick assembly as a contact medium to concurrently apply the liquid onto the intermediate transfer support surface and to remove foreign matter from the support surface. Specifically, as the support surface or transfer drum rotates, the wick assembly is moved into stationary contact with the rotating transfer drum. In this manner, relative motion is created between the rotating transfer drum and the stationary wick such that the transfer drum brushes or rubs against the wick. This allows the wick to contact and remove foreign matter and debris from the drum. However, it also allows debris to accumulate at the point of contact between the drum and the wick, which can interfere with the application of liquid to the drum. This applicator assembly also includes a hydrodynamic wiper blade that uniformly meters and distributes the liquid intermediate transfer surface over the transfer drum.
In the 645 patent, a supply of liquid for the wick is maintained in two separate oil filled bladders adjacent to the applicator assembly. The release of the oil from the oil bladders is actuated by the movement of the wick assembly upwardly along a valve opening track as the wick assembly moves toward the transfer drum support surface. This movement opens a valving system that allows oil to flow from the bladders through oil access cross bores and spool valve bodies and into a channel that contains the wick. From the channel the oil is wicked upwardly to the upper portion of the wick that contacts the transfer drum.
In the 645 patent, prior to installation of the drum maintenance cassette in a printer, the wick is dry, the valving system is closed and the oil does not flow from the bladders to the wick. Upon insertion of the cassette into a printer, the valving system is opened as described above and the oil begins flowing to the wick. To allow the wick to become sufficiently saturated with the oil for proper operation, printing is disabled for a predetermined period, designated the “time-to-first-print,” after a new cassette is inserted in a printer.
U.S. Pat. No. 6,068,372 to Rousseau et al. (hereinafter “the 372 patent”) also discloses a replaceable liquid application system for applying a liquid intermediate transfer surface to a support surface in a printer. The liquid application system is contained in a removable cassette and utilizes a liquid impregnated arcuate surface that engages the support surface by rolling contact. The liquid impregnated arcuate surface is contained in a removable cartridge in the cassette. A cartridge life status assembly determines when the useful life of the cartridge has been exhausted. Push tabs on the cartridge and finger wells on the cassette allow for easy and convenient removal of a used cartridge and insertion of a replacement cartridge.
In the 372 patent, the cartridge also contains a reclamation assembly that extends the useful life of the cartridge. The reclamation assembly reclaims liquid from the support surface, filters the liquid by passing the liquid over a filter and supplies the liquid back to the arcuate surface for reapplication to the support surface. Over time, however, the filter is clogged with debris. Once it becomes too clogged the system will operate as if the filter did not exist, thus allowing debris to clog the roller.